For one night only, Pauline Collins, Lesley Ann Down and Jean Marsh will take to the stage alongside other stars to perform material from the drama.
The Bafta and Emmy award-winning series, which ran from 1971 to 1975, was set in a large Edwardian townhouse in London and depicted the lives of the servants "downstairs" and their masters "upstairs".
Hosts of the Happy Birthday Bafta evening Michael Parkinson and Joanna Lumley will be joined by a wide range of performers including Liza Minnelli, Celine Dion, operatic star Andrea Bocelli, and stars from West End shows Billy Elliott and Cabaret.
Veteran comedian Ronnie Corbett will appear, with comedy duo Armstrong and Miller recreating a classic Morecambe and Wise sketch. Cast members from five decades of Coronation Street will be brought together on stage and twelve-time Bafta winner Victoria Wood will close the show with a special performance.
The event is being held on October 28, with ITV1 broadcasting the show next month.